Method for operating a coke oven arrangement

ABSTRACT

The invention pertains to a method for operating a coke furnace arrangement, wherein the coke oven gas accumulated during the coking process is utilized as a working gas. According to the invention, a synthesis gas produced from fossil fuel, preferably coal, by means of a gasification process is supplied as fuel gas in order to provide at least part of the thermal energy required for the coking process.

The invention pertains to a method for operating a coke oven arrangement, wherein the coke oven gas accumulated during the coking process is utilized as a working gas.

In practical applications, the coke oven gas accumulating during a coking process is usually burned and therefore only utilized energetically although coke oven gas contains large amounts of the valuable components hydrogen and methane. The main reason for reservations against such utilization is that the coke oven gas is no longer available as a heating gas and the lacking heating energy needs to be provided otherwise.

DE 34 244 24 A1 discloses a method, in which the coke oven gas accumulating during a coking process is utilized in the form of a working gas. In this case, hydrogen is extracted and a suitable H₂—CO ratio is adjusted in order to subsequently produce a synthetic natural gas by means of methanation. Since the coke oven gas is no longer available for generating the thermal energy required for the coking process during this utilization, it is proposed to use blast furnace gas or methane as substitute gas for the undergrate firing of the coke oven gas battery. The use of blast furnace gas or methane may be considered if a steel mill or a coal mine is located in the immediate vicinity of the coke oven plant and the use of these substitute gases proves to be economical. Since these requirements only are rarely fulfilled in practical applications, the coke oven gas usually is only utilized for heating purposes as mentioned above.

Other methods for utilizing coke oven gas are known from DE 35 15 250 A1 and DE 38 05 387 A1. In these methods, it is respectively proposed to mix the coke oven gas that has a high hydrogen content with blast furnace gas that has a high carbon monoxide content. The known methods require that blast furnace gas, which initially needs to be elaborately cleaned, is available in sufficient quantities.

The present invention is based on the objective of allowing a flexible and efficient utilization of the coke oven gas accumulating during the operation of a coke oven arrangement.

This objective is attained with the object of the invention, namely a method for operating a coke oven arrangement with the initially described characteristics, characterized in that for providing at least a part of the thermal energy necessary for the cooking process, a synthesis gas is being fed as a fuel gas, the synthesis gas being produced from fossil fuel by means of a gasification process. A particularly high flexibility of the method for operating a coke oven arrangement is achieved due to the utilization of a fossil fuel for producing the synthesis gas. Although making available the fossil fuel and carrying out the gasification process for producing the synthesis gas is associated with additional investment and process costs, economical advantages are achieved due to the recovery of the valuable components contained in the coke oven gas. This applies, in particular, if coal is used as fossil fuel because coal is inexpensive in comparison with other fossil fuels suitable for carrying out the gasification process, e.g., natural gas, and already kept on hand for carrying out the coking process anyway. Consequently, the inventive method can be used independently of other production sites such as coal mines or blast furnaces. However, if a blast furnace plant is located in the immediate vicinity, it is also possible to thermally utilize another portion of the synthesis gas being produced in a blast furnace.

According to the invention, it is proposed to extract the gas components such as hydrogen and/or methane that accumulate in the coke oven gas during a coking process and to either utilize these gas components as an end product or to convert the gas components into products of even higher value, wherein the lacking amount of energy for the coking process and possibly also a blast furnace process is replaced with the synthesis gas produced from the fossil fuel by means of gasification. The crude synthesis gas being produced usually only needs to be desulfurized before it can be utilized as fuel gas in order to provide part of the thermal energy required for the coking process, particularly for the undergrate firing of coke oven batteries. The synthesis gas used as fuel gas does not require elaborate processing that, among other things, also includes the removal of carbon dioxide.

According to the invention, the synthesis gas produced from the fossil fuel may be exclusively utilized as fuel gas in order to generate thermal energy. According to one preferred embodiment of the invention, however, the quantity of synthesis gas being produced exceeds the quantity required as a substitute for the coke oven gas utilized in accordance with the invention. It may be provided that a first portion of the synthesis gas being produced is utilized as fuel gas and another portion of the synthesis gas being produced is used for an additional conversion and subsequent utilization.

In the inventive method, impurities such as tar, naphthalene, aromatic hydrocarbons (BTX-components), sulfur and ammonia are initially removed from the coke oven gas accumulating during the coking process analogous to a conventional coking process known from the state of the art. According to one preferred embodiment of the invention, the thusly cleaned coke oven gas is compressed in order to extract hydrogen and/or hydrocarbons. In order to extract hydrogen, it would be possible, for example, to carry out a pressure swing adsorption (PSA) in a PSA-system, wherein the hydrogen is extracted in highly pure form on the pressure side of the PSA-system. The pressure swing adsorption may be carried out in a conventional PSA-system or in a vacuum PSA-system (VPSA-system).

A methane-rich gas is obtained on the expansion side of the PSA-system and separated from the remaining gas components, particularly carbon monoxide (CO), carbon dioxide (CO₂), nitrogen, acetylene and residual hydrogen. The removal of nitrogen, carbon monoxide and residual hydrogen may be realized, for example, by means of a low-temperature distillation, wherein carbon dioxide and water vapor previously need to be removed with suitable methods such as, e.g., amine scrubbing and/or molecular sieve drying. The hydrocarbon components thusly recovered as working gas can be supplied to a natural gas network and/or kept on hand for another synthesis.

As mentioned above, the gas components recovered from the coking gas can be used as end products or converted into products of even higher value, wherein a portion of the synthesis gas produced during the gasification of the fossil fuel can also be used for another synthesis and conversion. Advantageous optional utilizations are described below.

The extracted hydrogen can be generally utilized as hydrogenating hydrogen in adjacent chemical plants such as, for example, refineries. According to one preferred embodiment, it is proposed to subject the produced hydrogen and a portion of the synthesis gas produced due to the gasification of the fossil fuel to an additional conversion, wherein the hydrogen is converted into products of higher value with a portion of the carbon monoxide of the synthesis gas. It would be possible, for example, to carry out a synthesis of methanol, as well as the further production of fuel, by means of an MTG-method (methanol to gasoline), the synthesis of diesel according to a Fischer-Tropsch method or even the synthesis of ammonia.

If the extracted hydrogen and the synthesis gas that is obtained from the fossil fuel and essentially contains carbon monoxide are used for another synthesis, it is advantageous that a specific hydrogen/carbon monoxide ratio can be freely adjusted within a broad range by means of a corresponding inflow control.

In order to additionally increase, in particular, the hydrogen yield of the entire method, it would be possible to subject a portion of the produced synthesis gas to a CO-conversion. For this purpose, the CO-conversion can be carried out with the addition of water vapor, wherein carbon dioxide is at least partially removed after a desulfurization of the converted synthesis gas, wherein the remaining gas flow is subsequently subjected to a pressure swing adsorption in order to remove hydrogen, and wherein the off-gas that is depleted of hydrogen and accumulates during this process is used as fuel gas for the coking process. This thermally utilized off-gas usually represents a portion of the overall fuel gas required for providing the thermal energy.

The synthesis gas obtained from the fossil fuel may also be utilized for generating power with a combined gas and steam turbine plant (GUD-process).

According to the invention, a portion of the thermal energy required for the coking process is provided by a synthesis gas in the form of fuel gas that is obtained from a fossil fuel by means of a gasification process, preferably by means of coal gasification. The residual gases and waste gases accumulating in the various subsequent process stages may also be used for burning in order to provide another portion of the thermal energy. The off-gas of the preferably used PSA-system, in particular, usually still has a high content of combustible components that can be thermally utilized by being burned. In addition, high-quality fuels with a higher calorific value such as, for example, natural gas can also be admixed. Such an admixing may be required for adjusting a desired Wobbe index or for compensating an energy demand that is not yet covered by the additional fuel gases. 

1. A method for operating a coke furnace arrangement, wherein the coke oven gas accumulated during the coking process is utilized as a working gas, wherein hydrogen is extracted from the coke oven gas, and wherein a synthesis gas produced from fossil fuel by means of a gasification process is supplied as fuel gas in order to provide at least part of the thermal energy required for the coking process, wherein a first portion of the synthesis gas being produced is utilized as fuel gas, and wherein another portion of the synthesis gas being produced is used for an additional synthesis with the hydrogen extracted from the coke oven gas.
 2. The method according to claim 1, wherein coal is used as fossil fuel.
 3. The method according to claim 1, wherein the coke oven gas is compressed and desulfurized before hydrogen is extracted therefrom and hydrocarbons are subsequently separated from residual gas components.
 4. The method according to claim 1, wherein hydrogen is extracted from the coke oven gas by means of pressure swing adsorption, wherein hydrocarbons are subsequently extracted by means of a low-temperature distillation.
 5. (canceled)
 6. The method according to claim 1, wherein a first portion of the synthesis gas being produced is used as fuel gas, and wherein another portion of the synthesis gas being produced is subjected to a CO-conversion.
 7. The method according to claim 6, wherein the CO-conversion is carried out with the addition of water vapor, wherein carbon dioxide is at least partially removed after a desulfurization of the converted synthesis gas, wherein the remaining gas flow is subsequently subjected to a pressure swing adsorption in order to remove hydrogen, and wherein the off-gas that is depleted of hydrogen and accumulates during this process is used as fuel gas for the coking process.
 8. The method according to claim 1, wherein a first portion of the synthesis gas being produced is used as fuel gas, and wherein another portion of the synthesis gas being produced is used for generating power in a combined gas and steam turbine plant.
 9. The method according to claim 1, wherein another heating gas is supplied in addition to the synthesis gas in order to provide the thermal energy required for the coking process.
 10. The method according to claim 1, wherein another portion of the synthesis gas being produced is supplied to a blast furnace in order to be thermally utilized. 